Plants of such type are described for example in the documents EP-0 343 061 and FR-2 514 669.
The corresponding apparatus ensure extraction of elements in suspension in a drawn atmosphere of particular premises, for example in production, treatment or storage facilities of powdery products, or of certain industries causing the release of waste such as very volatile sawings or chippings.
Such apparatus are formed conventionally of three main elements generally centred on the same vertical axis:
an upper body, cylindrical or truncated, wherein the air to be de-dusted arrives tangentially,
a settling chamber, in the form of a funnel or cylindrical, arranged beneath the upper body; this chamber is fitted with waste recovery means at the lower section thereof, and
a filter cartridge formed of vertical filter sleeves extending between said settling chamber and the cover of the apparatus where the filtered air is exhausted.
The corresponding filter sleeves are generally cylindrical in shape and they are made conventionally of a material such as needled felt. Such sleeves are stretched vertically within the filter cartridge between two adapted supporting structures: their lower ends are interconnected on a lower supporting structure, for example in the form of a grid, which is situated above the settling chamber, and which provides access to the contaminated air on the outer side of the filter sleeves; their upper ends are interconnected to an upper supporting structure, generally in the form of a plate fitted with circular openings, for exhausting the air filtered.
The assembly of each filter sleeve within this kind of plant is described for example in the document U.S. Pat. No. 4,244,718. Such assembly consists first of all in interconnecting the upper end of the sleeves at one of the openings of the upper plate; such interconnection is obtained traditionally an integrated member in the form of a ductile ring (of <<snap ring>> type).
The lower end of the sleeves is then attached to the lower supporting structure; appropriate means are provided at this lower end for reliable tensioning of each sleeve.
By reason of the structure of the current filtration plants, the operator should be able to access the lower supporting structure to carry out most of the assembly and maintenance operations relative to the filter sleeves.
Still, the corresponding interventions are not really convenient because of the small space requirements encountered. Moreover, they are conducted in dusty and dirty environments; besides, they are not totally harmless to the operator further to the dusts in presence, in particular within the framework of items of equipment processing atmospheres with explosive or flammable characteristics.